Eight months after his death, a study of Junior Seau’s brain revealed the beloved former Charger suffered from a debilitating brain disease that may have contributed to personality changes and may have been a factor in his suicide.

“It certainly does provide the largest piece of the puzzle of all the whys we went through eight months ago,” said Gina Seau, Junior’s ex-wife. “It certainly explains a lot of his behaviors in the last several years.”

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Seau’s family donated his brain for study by the National Institutes of Health, which released a statement Thursday describing its findings.

Neuropathologists examined three different unidentified brains in a blind study and determined that Seau’s brain had symptoms consistent with chronic traumatic encephalopathy or CTE, a disease first described in studies of boxers who developed dementia and Parkinson’s disease-like symptoms.

Other former NFL players who have died, including some who have committed suicide, also have been found to have suffered from CTE.

The NIH statement said that in many cases, people with CTE were described as having undergone personality changes and suffered from depression, increased irritability and trouble with attention.

These symptoms are consistent with ways in which those close to Seau described him following his May 2 suicide, in which he shot himself in the chest at his Oceanside home. He was 43.

Seau grew up in Oceanside and played 12 seasons for the Chargers, then eight more for the Miami Dolphins and New England Patriots. He retired after the 2009 season. According to those close to him, Seau increasingly suffered from insomnia, depression, anxiety, alcohol abuse, mood swings and emotional detachment, among other things, throughout most of his career and after his retirement in January 2010.

“Looking back,” Sydney Seau, Junior’s daughter, said Thursday, “I always wondered why he was so disconnected and why I had to have such an effort to talk to him and see him. I’ve always been his only girl and he’s been my guy. He never said ‘no’ to me, but the last couple years it’s been a struggle. It helps me, but it also hurts me to know he wasn’t to blame.“

The NIH noted that the “relationship between … CTE and the symptoms is poorly understood. Whether and how the … CTE progresses to the more extensive brain degeneration is still unclear.”

However, a renowned neurologist who studies the effects of brain trauma in athletes — especially in boxing and football — indicated the link is difficult to dispute.

“We never will definitely know, but the behavioral changes that he was experiencing could very well be secondary to CTE,” said Dr. Barry Jordan, assistant medical director and director of the brain injury program at the Burke Rehabilitation Hospital in White Plains, N.Y. “The behavioral dysfunction may be one of the early signs of CTE, so it is possible. His brain was abnormal. We know that from the autopsy. Mostly people agree that you could have behavioral problems from this syndrome.”

Seau never had a reported concussion during his career, although it is considered highly unlikely that he never experienced one. Jordan estimated an NFL player might experience as many as 1,000 subconcussions in a single season. He noted, however, that “we don’t know if a concussion causes CTE, or if subconcussive trauma does.”

For Seau’s family, the connection between Seau’s football career, the finding of CTE and his emotional and psychological struggles is plain.

“Logic tells me he played football for 20-plus years,” Gina Seau said. “He hasn’t done anything else, so what else could possibly have caused this?”

The NIH findings further highlight the ongoing fight to make football safer.

The NFL released a statement Thursday morning reiterating its commitment to brain trauma research.

“We appreciate the Seau family’s cooperation with the National Institutes of Health,” the statement read. “The finding underscores the recognized need for additional research to accelerate a fuller understanding of CTE. The NFL, both directly and in partnership with the NIH, Centers for Disease Control and other leading organizations, is committed to supporting a wide range of independent medical and scientific research that will both address CTE and promote the long-term health and safety of athletes at all levels.

“The NFL clubs have already committed a $30 million research grant to the NIH, and we look forward to making decisions soon with the NFL Players Association on the investment of $100 million for medical research that is committed in the Collective Bargaining Agreement. We have work to do, and we’re doing it.”

Later, the NFLPA released a statement reiterating its desire for the league to improve its oversight of head injuries and calling for a congressional review.

“We know that research and partnerships will be an important factor in improving player care and safety,” the NFLPA statement said. “We also know that accountability and credibility are equally important measures in the overall commitment to player safety. The only way we can improve the safety of players, restore the confidence of our fans and secure the future of our game is to insist on the same quality of medical care, informed consent and ethical standards that we expect for ourselves and for our family members. This is why the players have asked for things like independent sideline concussion experts, the certification and credentialing of all professional football medical staff and a fairer workers’ compensation system in professional football.”

Jordan, the brain expert, expressed confidence that the news regarding Seau, considered one of the greatest linebackers in NFL history, would help promote change.

“It is already one of the hottest topics in sports,” he said. “The results will keep this disorder in the forefront of scientific research. … I think it will raise everyone’s level of awareness. I think it will help make sports safer. The key is to diagnose this while the athlete is alive, and treat it, and prevent further injury to the brain, while he or she is alive. The results of Junior’s brain study came as no shock, but it’s unfortunate that the researchers came back with this.”

Gina and Sydney Seau hoped for the same, even as they repeatedly noted that these findings do nothing to stem their loss.

“The first thing that came to mind was, ‘OK, great, I’m glad we have some answers,’ ” Sydney said. “At the same time, I’m still filled with grief and I still don’t have him here next to me. … I’m glad this all came out, so we can spread awareness of CTE. At the end of the day, though, there is no remedy that brings him back.”